Drilling fluids and additives therefor



United States Patent 3,344,063 DRILLING FLUIDS AND ADDITIVES THEREFGRCharles A. Stratton, Copan, Okla, assignor to Phillips PetroleumCompany, a corporation of Delaware No Drawing. Filed Sept. 30, 1965,Ser. No. 491,837 Claims. (Cl. 252-85) This application is acontinuation-in-part of my copending application Ser. No. 258,888, filedFeb. 15, 1963, now abandoned.

This invention relates to drilling fluids and additives therefor. In oneaspect this invention relates to drilling fluids having improved waterloss properties and/0r improved viscosity or other rheologicalcharacteristics. In another aspect this invention relates to an additivefor drilling fluids and a process for making same, which additive whenincorporated in a drilling fluid imparts improved water loss propertiesand/or viscosity or other rheological characteristics to said drillingfluid.

In the art of drilling wells to tap subterranean deposits of fluids suchas oil and/ or gas, especially when drilling by the rotary methodemploying a rotary bit and drill stem, a drilling fluid, usually acompounded fluid made to predetermined physical and chemical properties,is circulated to the bottom of the bore hole, out through openings inthe bit at the bottom of the bore hole, and then back up said bore holeto the surface by passage through the annular space between said drillstem and the Wall of said bore hole '(or between said drill stem and thewall of the casing where casing has been put in place).

The drilling fluid must act as a liquid medium of controlled viscosityfor removing cuttings from the bore hole; it must prevent excessiveamounts of fluid from flowing from the bore hole into surroundingformations by depositing on the wall of the hole a thin butsubstantially impervious filter cake; it must possess a gel structure ofsufficient strength to hold in suspension solids, particularly duringany time the fluid is not circulating; and it must serve as a weightingmaterial exerting suflicient pressure to counterbalance any pressureexerted by water, gas, oil, or other fluid from a penetrated structureand to prevent caving or other intrusion into the drill hole.

These requirements have been met in the past by employing both aqueousor water base and non-aqueous or oil base drilling fluids. The aqueousdrilling fluids normally comprise water, and finely divided inorganicmaterials such as various types of clays and clayey materials, and mayalso contain weighting materials, all suspended in the water. Thenon-aqueous or oil base drilling fluids normally comprise a non-aqueousliquid such as crude oil or a petroleum distillate, and a weightingmaterial which can be a clay or other suitable material. In addition toaqueous and non-aqueous drilling fluids as defined above, emulsion-typedrilling fluids are often used. These emulsion drilling fluids normallycomprise a substantially water-insoluble liquid such as oil, a finelydivided inorganic material such as clay, and water, together with asuitable dispersing or emulsifying agent. The two types of emulsiondrilling fluids are the oil-in-water emulsion type, sometimes referredto as water base emulsion type, and the water-inoil emulsion type,sometimes referred to as oil base emulsion type. In the latter, oilforms the continuous phase of the emulsion, and in the former, Water orbrine forms the continuous phase of the emulsion.

In the drilling of wells there are major difliculties caused by naturalformations penetrated. One of these difficulties is the encountering ofcertain formations, such as gypsum, which Will cut the drilling mud sothat the clay particles are flocculated and the viscosity becomes toohigh. In such instances there is danger of the drill pipe twisting inhalf, or of gas cutting of the mud, or of a 3,344,,fl63 Patented Sept.26, 1967 blowout occurring due to the cutting of the mud. Anotherdifficulty is the encountering of formations known as heaving shale. Aheaving shale absorbs water from the drilling mud and by a caving ordisintegrating action common to clay and shale, or by a swelling actioncommon to bentonite materials, the well hole is closed around the drillstring, choking off the circulation of drilling mud and often seizingthe drill string so that it cannot be rotated or twists in half. Anotherdifliculty which is frequently encountered in deeper wells is gelationand/ or thickening of the drilling mud due to the higher temperaturesencountered in said deeper wells. In such instances the drilling mudactually gels and/or thickens, greatly increasing the pump pressuresrequired for circulating the drilling mud. In severe cases it becomespractically impossible to properly circulate the mud. Furthermore, saidhigh temperature gelation is frequently aggravated by the presence ofcontaminants such as gypsum, salt, cement, etc., in the drilling mud.Thus, another requirement for drilling muds is that they becharacterized by stability at the higher temperatures encountered indeeper wells.

I have now discovered a new class of additives for drilling fluids,which additives when incorporated in aqueous drilling fluids, e.g.,water base drilling fluids and oil-inwater emulsion drilling fluids,impart enhanced water loss properties and/ or enhanced viscosity orother rheological characteristics to said drilling fluids. Said newadditives are metal complexes of sulfoalkylated tannin.

.Thus, broadly speaking, the present invention resides in said newadditives; methods for preparing said new additives; drilling fluidscontaining one or more of said new additives; and methods of using saiddrilling fluids in the drilling of wells.

Thus, an object of this invention is to provide an improved drillingfluid. Another object of this invention is to provide an improveddrilling fluid having enhanced water loss properties and/or enhancedviscosity or other rheological characteristics. Another object of thisinvention is to provide improved aqueous drilling fluids which arecharacterized by stability to the high temperatures encountered indrilling deep Wells. Another object of this invention is to provide newadditives for use in aqueous drilling fluids, e.g., water base drillingfluids and oil-inwater emulsion drilling fluids, which additives willimpart enhanced water loss properties and/or enhanced viscosity or otherrheological characteristics to said drilling fluids. Another object ofthis invention is to provide methods of preparing said new drillingfluid additives. Another object of this invention is to provide methodsof using said improved drilling fluids in the drilling or workover ofWells. Other aspects, objects, and advantages of the invention will beapparent to those skilled in the art in view of this disclosure.

Thus, according to the invention, there is provided an aqueous welldrilling fluid comprising: water; sufiicient finely divided solids toform a filter cake on the wall of the Well; and an amount of a metalcomplex of a sulfoalkylated tannin suflicient to reduce at least one of(a) the water loss due to filtration through said filter cake, (b) theyield point, and (c) the 10-minute gel, but insuflicient to increase theviscosity of said drilling fluid to such an extent that it cannot becirculated; said metal being selected from the group consisting of iron,copper, chromium, nickel, cobalt, manganese, zinc, aluminum, titanium,and vanadium.

Further according to the invention, there is provided an aqueous welldrilling fluid comprising a mixture containing: water; sufficientsuspended finely divided solids to form a filter cake on the wall of thewell; and an amount of a metal complex of a sulfoalkylated tanninsuflicient to reduce the water loss due to filtration through saidfilter cake but insufficient to increase the viscosity of said drillingfluid to such an extent that it cannot be circulated; said metal complexhaving been prepared by the interreaction, in an alkaline aqueousreaction medium under reaction conditions, between a tannin compound, acarbonyl compound selected from the group consisting of the lowermolecular weight aldehydes and ketones, a sulfur compound selected fromthe group consisting of sulfurous acid and water-soluble salts thereof,and a metal compound selected from the group consisting of thehydroxides and water soluble salts of iron, copper, chromium, nickel,cobalt, manganese, zinc, aluminum, titanium, and vanadium.

Further according to the invention, there are provided methods of usingthe improved well drilling fluids of the invention, which methodscomprise circulating said well drilling fluids into and from the borehole in contact with the walls of said bore hole.

Still further according to the invention, there are provided as newcompounds, metal complexes of sulfoalkylated tannins, and methods ofpreparing same, as discussed further hereinafter.

The metal complexes of sulfoalkylated tannins which are the newadditives of the invention are preferably those which are soluble in thewater phase of the drilling fluid. However, as discussed furtherhereinafter, the invention is not limited to the metal complexes ofsulfoalkylated tannins which are completely soluble in water. It issufiicient if said metal complexes can be readily dispersed in the Waterphase of the drilling fluids in any suitable manner.

Examples of metal compounds which can be used in the preparation of themetal complexes of the invention, include, among others, thewater-soluble salts such as the nitrate or chloride, and the hydroxidesor hydrated oxides of iron, copper, chromium, nickel, cobalt, manganese,zinc, aluminum, titanium, and vanadium. Generally speaking, thewater-soluble salts are preferred. However, the hydrated oxides orhydroxides of said metals are sometimes preferred compounds for use inthe practice of the invention because they contain no anions such aschloride or nitrate which would be left in the reaction mixture when thecation is complexed with the tannin. Another preferred class ofmetal-containing compounds which can be used in the practice of theinvention are the ammonium and the alkali metal salts of the abovemetals wherein the said above metals are present in the anion portion ofthe molecule, e.g., the alkali metal chromates, vanadates, titanates,manganates, etc., and the alkali metal dichromates. As used herein andin the claims, unless otherwise specified, the term alkali metal isemployed generically to include sodium, potassium, lithium, rubidium,cesium, and ammonium.

Tannins which can be used in preparing the metal complexes ofsulfoalkylated tannins in accordance with the invention are thevegetable tannins, including both the gallotannins and the flavotannins,(sometimes called catechol tannins). Thus, the word tannin as usedherein and in the claims, unless otherwise specified, refers to andincludes the vegetable gallotannins and the vegetable flavotannins.Examples of the gallotannins include: tannic acid or Chinese tannin,Turkish tannin, Hamamelis tannin, Acer-tannin, Glucogallin, sumactannin, Valonia oak gall tannin, tea tannin, tara, myrabolam, divi-divi,algarobilla, oak, and chestnut. Examples of flavotannins include:gambier and catechu or Burma cutch, quebracho, Tizerah, urunday, wattle,mangrove, spruce, hemlock, larch, willow, and avaram. Said flavotanninsare the preferred tannins for use in the practice of the invention.

Quebracho is the presently most preferred tannin for use in the practiceof the invention. Quebracho is extracted from the bark and wood of thequebracho tree with water. The conventional method of preparingquebracho is to disintegrate the wood and bark, extract the bark and/ orwood with water, the solution of quebracho and water is evaporated to 85percent concentration of quebracho and the concentrated quebracho isspray dried. Quebracho is the commercial catechol tannin or flavotanninproduct. The high tannin content (about 20 percent) of the wood of thequebracho tree makes it the important source of catechol tannins. Theprincipal source of gallotannins is gall nuts.

The metal complexes of sulfoalkylated tannin, either a gallotannin or aflavotannin, can be prepared by several different procedures, all inaccordance with the invention. All of said procedures involve theinter-reaction, in an alkaline aqueous reaction medium under reactionconditions, between a tannin compound, a carbonyl compound selected fromthe group consisting of aldehydes and ketones, a sulfur compoundselected from the group consisting of sulfurous acid and water-solublesalts thereof, and a metal compound selected from the group consistingof the hydrated oxides or hydroxides and the water-soluble salts ofiron, copper, chromium, nickel, cobalt, manganese, zinc, aluminum,titanium, and vanadium. Thus, in one method in accordance with theinvention, an alkali metal hydroxide, e.g., sodium hydroxide, analdehyde or ketone, e.g., formaldehyde or acetone, a sulfite, e.g.,sodium sulfite or sodium bisulfite, a tannin, e.g., quebracho (quebrachoextract), and a suitable metal compound, e.g., ferric hydroxide, areadded to water in a reaction vessel to form a reaction mixture. Thesequence of adding said reactants to the Water is not critical. However,it is sometimes preferred to add the alkali metal hydroxide first. Theamount of alkali metal hydroxide employed will be an amount sufficientto make the reaction mixture alkaline, at least initially. Said reactionmixture is then maintained under conditions of time and temperaturesufiicient to cause the substantial conversion of the tannin compoundinto a metal complex of sulfoalkylated tannin.

If desired, the carbonyl compound, e.g., formaldehyde or acetone, andthe sulfite can be prereacted. Thus, in one method, for example, asolution containing formaldehyde and sodium sulfite is preparedseparately and then combined with the other reactants in the alkalinereaction medium.

In one preferred method for preparing the metal complexes of theinvention, an alkaline first solution is prepared by dissolving a tannin(such as quebracho extract), and an alkali metal hydroxide (such assodium hydroxide) in water. A second solution is formed by admixing acarbonyl compound (such as formaldehyde) and a sulfite (such as sodiumbisulfite) in water. Said second solution is then added to said firstsolution to form a third solution. Said third solution is thenmaintained at an elevated temperature for a period of time suflicientfor at least a substantial portion of said aldehyde and said sulfite toreact with said tannin to form a sulfoalkylated tannin. A metal compound(such as ferric hydroxide) is then added to said third solution andreacted with the sulfoalkylated tannin therein to form a metal complexof sulfoalkylated tannin which is recovered from the resulting reactionmixture. In this instance, using the exemplary reactants mentionedabove, the product is an iron complex of sulfomethylated quebracho.

In another preferred method for preparing the metal complexes of theinvention, the desired amount of water is added to a reactor vesselequipped with suitable stirring means. The desired amount of carbonylcompound (such as formaldehyde) is then added to said Water withstirring. The desired amount of a sulfite (such as sodium bisulfite) isthen added to the water, with stirring, and the carbonyl compound andsulfite are permitted to react to completion. Usually the reaction timewill be within the range of 0.5 to 3 hours and the final temperaturewill be in the order of F., depending upon the initial ambienttemperature of the water, the amount of reagents, etc. The desiredamount of an alkali metal hydroxide (such as sodium hydroxide) is thenadded. The tannin compound (such as quebracho) is then added to the tankcontaining the above reagents with vigorous stirring. Heating isinitiated and the solution is maintained at an elevated temperaturewhich is preferably within the range of 180 to 200 F. for a period offrom 1 to 6 hours. The desired amount of a metal compound is then addedto the solution of sulfoalkylated tannin and reacted therewith to form ametal complex of sulfoalkylated tannin. It is not necessary to addadditional heat to the reactant solution during the addition of themetal compound. The residual heat remaining from dissolving the tannincompound will usually be sufiicient. After the sulfoalkylation reactionis complete the metal complex of sulfoalkylated tannin is recovered fromthe reaction solution in any suitable manner, such as by drum drying orspray drying.

If desired, the metal can be complexed with the tannin compound first.In this method, the metal compound is added to an alkaline solution ofthe tannin to form the metal complex of said tannin. Said metal complexis then sulfoalkylated by adding the carbonyl compound and sulfite,either prereacted or not prereacted, to the solution of the metalcomplex of the tannin to sulfoalkylate said metal complex and form ametal complex of sulfoalkylated tannin.

In all of the above methods for preparing the additives of theinvention, the metal complexes of sulfoalkylated tannin can be recoveredfrom the reaction mixture by any suitable method such as evaporation,drum drying, spray drying, etc. It is not essential to recover saidmetal complexes of sulfoalkylated tannin from the reaction mixture. Saidreaction mixture can be used per se in liquid form in the drillingfluids of the invention. However, it is preferred to recover and drysaid metal complex products. The dried solids can then be bagged andshipped to the field for use in the drilling muds described herein.

The vegetable tannins are high molecular weight materials havingmolecules of complex structure containing phenolic hydroxyl groups. Someauthorities consider said tannins to be mixtures of polyphenolicsubstances. So far as is known all of said tannins contain at least onearomatic (e.g., benzene) ring having at least one phenolic hydroxylgroup attached thereto. Said hydroxyl groups have their hydrogen atomsreplaced in alkaline solution. It is believed the hydroxyl groupsfurnish at least a portion of the reactive sites for complexing an atomof a metal such as iron with the tannin molecule. The reactive sitesremaining on the aromatic ring structure are susceptible tosulfoalkylation to add side chain(s) to the tannin molecule.

Due to the complex nature and chemistry of the tannin compounds it isnot intended to limit the invention to the above or to any specificreaction mechanism, or to any specific method for preparing theadditives of the invention. However, said additives of the invention canbe conveniently described in terms of processes for their manufacture.One reaction mechanism by which the product additives of the inventioncan be formed is as follows. Two reactions, which can be carried outsimultaneously or-in any order, are involved, (1) a metal complexingreaction whereby an atom of the metal involved complexes with one, two,or three tannin molecules and (2) a sulfoalkylation reaction whereby thetannin molecule is alkylated by one or more sulfoalkylene radicalsattached to said tannin molecule as side chains. The alkylene portion ofsaid sulfoalkylene radical is a methylene or substituted methylenegroup. Thus, said side chain(s) can be represented by the formula C('R)SO M wherein each R is selected from the group consisting of a hydrogenatom and alkyl, cycloalkyl, aryl, and alkaryl radicals, and M isammonium or an alkali metal depending upon the particular sulfiteemployed. As indicated hereinafter, it is preferred when R is other thanhydrogen, that said R be an alkyl group containing from 1 to 5 carbonatoms.

As indicated above, the reactions involved in the preparation of theadditives of the invention are carried out in an alkaline aqueousmedium. Hydroxide's of the alkali metals sodium, potassium, lithium,rubidium, and cesium can be used to make said medium alkaline. Theamounts of said hydroxides used can be varied over a wide range. Theprincipal function of said hydroxide is to impart sufficient initialsolubility to the raw tannin so that it can react with the sulfite andaldehyde or ketone reactants and the metal compound in thesulfoalkylation and metal complexing reactions. In order to obtainpractical reaction rates for said reactions, the pH of the reactionmedium should be about 10. In any event, enough of the hydroxide is usedto make the initial pH of the reaction medium at least 7, and preferably10 to 13. However, large excesses of the hydroxide above the amountrequired to initially solubilize the raw tannin should be avoided forbest results. After the tannin has been sulfoalkylated it is notnecessary that the reaction medium be alkaline. Depending upon theparticular metal compound used to supply the complexing metal, the finalreaction mixture can have a pH of less than 7. When sulfurous acid and abisulfite is used as the sulfur compound, sufficient hydroxide should bepresent to convert these to the sulfite form. If desired, the alkalimetal hydroxide can be prereacted with the tannin prior to the additionof the other reactants to the reaction medium.

Carbonyl compounds which can be used in the practice of the inventioninclude any aldehyde or ketone containing a C=O group, the carbon atomof which is capable of becoming a methylene or substituted methylenegroup. Thus, aldehydes and ketones which can be used can be representedby the formula (R) C=O wherein R is as defined above. Since said R isnon-functional in the reaction, there is no real limit on what it is orthe number of carbon atoms which it contains. However, when R is undulylarge, solubility problems in the aqueous reaction medium and also inconnection with the solubility of the reaction product are encountered.The larger R groups tend to make the product hydrophobic. In general,this is undesirable when the products are used as the additives in thedrilling fluids of the invention. Thus, since it is preferred to carryout the reaction in an aqueous medium, it is preferred as a practicalmatter that when R is not hydrogen, it is an alkyl group containing from1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms.

Examples of said preferred aldehydes and ketone include:

formaldehyde acetone acetaldehyde methyl ethyl ketone propionaldehydediethyl ketone n-butyraldehyde methyl n-propyl ketone isobutyraldehydemethyl isopropyl ketone n-valeraldehyde The sulfur compound used in thepractice .of the invention is, in general, sulfurous acid and itswater-soluble salts such as the alkali metal salts and including theammonium salts. The alkali metal (as defined above) sulfites arepreferred. It is pointed out that when a bisulfite or sulfurous acid isadded to the alkaline reaction medium, it will be converted to asulfite. Therefore, herein and in the claims, 'unlem otherwisedesignated, the term sulfite is employed generically to includesulfurous acid and bisulfites which, when added to the alkaline reactionmedium, will be converted to and react as sulfites.

The amounts of the above-described reactants which are used are notcritical. So long as a significant amount of each of said reactants ispresent, the desired rections will proceed to some extent and some yieldof metal complex of sulfoalkylated tannin will be obtained. The amountsof each reactant used will depend upon the amount, the kind of tannin,and the percentage of conversion of said tannin which is desired. Forresults approaching the optimum, it is preferred to use amounts of saidreactants which are within the range of from 0.5 to 1.5 times thestoichiometric equivalent amount of each reactant which is required tocompletely react the tannin. Amounts of said reactants which are lessthan stoichiometric result in less than 100 percent conversion. Amountsin excess of stoichiometric result in a waste of material. Thus, it ispreferred to use substantially stoichiometric equivalent amounts of saidreactants. For example, the amount of sulfite and aldehyde or ketone ispreferably the stoichiometric equivalent amount required in thesulfoalkylation reaction. When the aldehyde or ketone and the sulfiteare prereacted, they are preferably prereacted in stoichiometricequivalent amounts. The amount of the iron or other metal compound usedis preferably an amount which is stoichiometrically equivalent to thatrequired to completely complex the tannin.

From the above it is seen that specific numerical ranges for the amountsof said reactants will be of only limited value in teaching thisinvention and it is to be understood the invention is not limited to anysuch specific numerical ranges. Those skilled in the art can readilydetermine from a few pilot experiments the stoichiometric amounts ofreactants required for the particular tannin being reacted. However, asan aid to those less skilled in the art, the following ranges, basedupon the specific examples given hereinafter were set forth in saidcopending application.

TABLE I.AMOUNT OF REAGENTS PER 100 LBS. OF TANNIN Reagent Broad Range,Preferred lbs. Range, lbs.

Alkali metal hydroxide -60 -30 Sulfite 4-115 -70 Aldehyde or Ketone 1-355-30 Oomplexing Metalz" Cr, Ni, Co, Mn, 4-33 9-28 All above metals 4-559-46 Calculated as the metal.

However, the ranges set forth in the following Table I-A are presentlymore preferred.

TABLE LIL-AMOUNTS OF REAGENTS PER 100 LBS. OF TANNIN Calculated as themetal.

The above preferred amounts of reactants can be stated in other ways.For example, in working with the amounts shown in the above Table I-A,the preferred amount of metal complexing agent (calculated as the metal)to be added to the sulfoalkylated tannin is in the range of from to 3,preferably to l, more preferably to mols of metal per monomer mol ofactive ingredient in the particular tannin compound being used. In otherwords, it is preferred that no excess metal be present in the reactionmixture at the conclusion of the metal complexing reaction. For example,when quebracho extract is the tannin being used, quebracho catechin isconsidered to be the active ingredient of the quebracho. Based on amolecular weight of 274 for said quebracho catechin, 100 pounds ofquebracho extract will contain an average of 0.33 pound mols ofquebracho catechin, and the preferred range of reagents given in column3 of the above Table I-A has been established on this basis. When othertannin materials are used, the molecular weight of the active ingredientthereof, as well as the amount contained per pounds of tannin, may bedifferent. Thus, it is desirable that the quantities of reagents to beused be established for each particular tannin material used. Thoseskilled in the art will have no difliculty establishing the amounts ofreagents to use in view of this disclosure. Any large deviation from the0.33 mol of active ingredient in any individual lot of quebracho extractwould also require an adjustment of the chemicals used for reacting withsaid quebracho. However, analyses of six commercially availablequebracho extracts available from different sources has shown thatcommercial quebracho extract is surprisingly uniform in composition.

The amount of carbonyl compound, e.g., formaldehyde, and the amount ofsulfite compound, e.g., sodium bisulfite, used in the reaction willdetermine the amount of sulfoalkylation of the tannin compound whichoccurs. This affords another way of expressing the amount of carbonylcompound and sulfite. The amount of sulfoalkylation which occurs in anygiven reaction situation can be expressed in terms of the parts byweight of the carbonyl compound-sulfite addition product orsulfoalkylation reagent, e.g., NaSO CH OHf0rmed by reactingstoichiometric amounts of formaldehyde and sodium bisulfite, used per200 parts by weight of tannin. For example, expressed in this manner andwhen using formaldehyde, sodium bisulfite, and quebracho, the mostpreferred amounts of sodium formaldehyde bisulfite addition product willbe within the range of from 50 to parts by weight of thesulfomethylation reagent per 200' parts by weight of quebracho.

In general, the reaction conditions are not critical. All the reactionsinvolved in the practice of the invention will take place at ordinaryroom temperatures (70-80 F.) but at a reduced rate and all reactionconditions at which the reactions will take place are within the scopeof the invention. However, as a practical matter, is is preferred toemploy elevated temperatures to cause said reactions to take place inless time. Any suitable temperature below the decomposition temperatureof the tannin can be employed. For example, the application of heat aidsin dissolving quebracho in the alkaline medium. As a general rule,temperatures in the order of 125 to 212 F. are suflicient. However,usually a more preferred range is from 180 to 212 F. If desired, thereaction mixture can be refluxed at atmospheric pressure, or can beheated in an autoclave under superatmospheric pressure to obtain highertemperatures. In general, the maximum temperatures employed will be inthe order of 300 F. Thus, an over-all numerical range for the reactiontemperatures can be said to be from 70 to 300 F.

The reaction time will be dependent upon the reaction temperatureemployed. Reaction times in the order of 0.5 to 10 hours have been foundquite sufficient. Preferably, the reaction times will be within therange of 1 to 6, more preferably 1 to 4, hours.

The amount of the metal complex additives of the invention used indrilling fluids in accordance with the invention will vary from well towell depending upon conditions encountered in the drilling of the well,the characteristics of the particular drilling fluid being used, theformations being drilled, etc. For example, as the drilling of the wellprogresses and the well becomes deeper and temperatures in the wellincrease, or the drilling fluid becomes contaminated, more additive willusually be required because of said increased temperatures and/orcontamination. While therefore the amount of additive used is not of theessence of the invention, it can be stated that the amount of saidadditive used will normally be within the range of 0.1 to 30, preferably0.1 to 15, and more preferably 1 to 15, pounds per barrel of drillingfluid. However, it is within the scope of the invention to employamounts of the additive which are outside said ranges. For example, theamount of additive used will always be an amount which is sufficient toreduce the water loss due to filtration and/ or effect an improvement orreduction in the rheological properties of the drilling fluid such as adecrease in yield point, 10-minute gel, or shear strength. As usedherein and in the claims, unless otherwise specified, the word barrelrefers to a barrel of 42 standard U.S. gallons.

The following examples will serve to further illustrate the invention.In the following examples the additives of the invention were tested inseven difierent base muds. These base muds were all prepared inconventional manner. In general, the method of preparation of said basemuds comprised preparing said muds in five-gallon batches in a suitableblending mill such as a Lear Blend-A Mill. The prepared muds werestirred for at least 30 minutes or more then aged for three days or moreprior to use. The compositions of said base muds are set forth in thefollowing examples and/ or in the tables setting forth the results ofsaid examples. In these examples sulfomethylated quebracho is sometimesreferred to as SMQ, for convenience. Similarly, the metal complexadditives of the invention are sometimes referred to as SMQ-metalcomplexes. For example, the iron complex of -sulfo methylated quebrachois referred to as SMQ-Fe, the copper complex as SMQ-Cu, etc.

Example I An iron complex of sulfomethylated quebracho was prepared asfollows: 200 grams of ground commercial quebracho extract (11.9 wt.percent water), 500 ml. of water, and 100 ml. of sodium hydroxide (0.5g. NaOH per ml.) were placed in a beaker and heated to a temperature ofabout 190 F. to dissolve said quebracho. A second solution was preparedby mixing 104 grams of sodium bisulfite, 89.3 ml. of 36 percentformaldehyde solution, and 500 ml. of water in a separate beaker. Thelatter solution was mixed and allowed to react for approximately 30minutes using no external heat source. Said two solutions were thenmixed and maintained at a temperature of approximately 160 F. for about1.5 hours. The resulting solution was then drum dried to recover asulfomethylated quebracho product.

(0.5 g. NaOH per ml.) were mixed in a first beaker and heated for onehour with stirring at a temperature of 190 F. in order to dissolve thequebracho and form a first solution. A second solution was formed byadding 208 grams of sodium bisulfite and 178.6 ml. of 36 percentformaldehyde solution to 750 ml. of water. The mixture was allowed toreact for minutes, using no external heat source. Said second solutionwas then added to said first solution and the combined solution washeated on a hot plate for about 4 hours during which time thetemperature was increased from 122 F. to 211 F.

Freshly precipitated ferric hydroxide was prepared by dissolving 135.15grams of FeCl -6H O in 2.5 liters of water and precipitating saidhydroxide by adding 150 ml. of concentrated ammonia solution. Theresulting precipitate was filtered and washed, and then added to saidcombined first and second solutions. The resulting mixture was heatedwith stirring for 2.5 hours at a temperature of ISO-190 F. and the ironhydroxide precipitate was taken into solution. The resulting solutionwas then evaporated on a drum drier to recover the dry product, an ironcomplex of sulfomethylated quebracho.

Example III A base mud having a composition of pounds of McCracken clayper barrel of water was prepared in conventional manner. Samples of saidbase mud containing 4 and 8 pounds per barrel respectively of the ironcomplex of sulfomethylated quebracho product of Example I per barrel ofsaid mud were prepared for tests. A second set of samples of said basemud containing 4 and 8 pounds per barrel respectively of the ironcomplex of sulfomethylated quebracho product of Example 11 were alsoprepared for tests. API Code RP-13B properties were then determined oneach of said samples with a Model 35 Fann V-G multi-speed viscosimeterand filter presses. The procedure for determination of API Code RP-l3Bproperties employing the Fann V-G viscosimeter is described by Chisholmand Kohen, Petroleum Engineer, 26 (4), B87 to B-90 (April 1954). Theresults of said tests are set forth in Table II below.

TABLE IL-ADDITIVES IN BASE MUD N0.Rl (50 LBS/BBL. MCCRACKEN CLAY IN WATEA*=Iron complex of suliomethylated quebracho prepared in Example I.B*=Iron complex of sulfomethylated quebracho prepared in Example II.

Freshly precipitated iron hydroxide was prepared by dissolving 7.6 gramsof FeCl -6H O in water and precipitating said hydroxide by the additionof ammonia. The precipitate was filtered and washed. A solution'of saidsulfomethylated quebracho product was prepared by dissolving 20 grams ofsame in water. Said precipitated ferric hydroxide was then added to thesulfomethylated que- Ibracho solution, and the resulting solution washeated and maintained at a temperature of about 160 F. for 1.5 hours.The solution was then dried on a hot plate under a heat lamp. The dryproduct, an iron complex of sulfomethylated quebracho, was then ground.

Example 11 Another iron complex of sulfomethylated quebracho wasprepared as follows: 233 grams of ground commercial quebracho extract(11.9 wt. percent water), 500 ml. of water, and 100 m1. of sodiumhydroxide solution Example IV formaldehyde solution, and 500 ml. ofwater in a sepa-- rate beaker, and allowing the mixture to react for 30minutes at room temperature. Said two solutions were then mixed andheated for 3 hours at 205 F.

Freshly precipitated iron hydroxide was prepared by dissolving 50 gramsof FeCl -6H O in water and precipitating said hydroxide by the additionof concentrated ammonia solution. The resulting precipitate was filteredand washed, and then added to the above-combined first cent kaolin and 4weight percent bentonite in water was prepared in conventional manner.Samples of said base mud containing 3 and 6 pounds per barrelrespectively of the sulfomethylated quebracho product of Example I wereprepared for tests. Samples of said base mud containing 3 and 6 poundsper barrel respectively of the iron complex of sulfomethylated quebrachoproduct of Example IV were also prepared for tests. Samples of said basemud containing 3 and 6 pounds per barrel respectively of the ironcomplex of sulfomethylated quebracho product of Example I were alsoprepared for tests.

and second solutions. The resulting mixture was heated, with stirring,for two hours at a temperature of 200'205 and the iron hydroxideprecipitate was taken into solution. The resulting solution was thenevaporated on a drum drier to recover the dry product, an iron complexof sulfomethylated quebracho.

Example V A base mud having a composition of 20 weight per- All of saidsamples were then tested for API Code 29 properties in accordance withthe procedure employed in Example III. The results of said tests aregiven in Table III below.

TABLE III.ADDITIVES IN BASE MUD NO. 2 (20 WT. PERCENT KAOLIN AND 4%BENTONITE IN WATER) I 2 Example VII A series of additives in accordancewith the invention was prepared. The amounts of reagents used and reaction conditions employed in preparing said additives are set forth inTable V below. All of said additives were prepared in the same generalmanner. Generally speaking, the method of preparation was as follows.The indicated amount of water was added to a suitably-sized reactionvessel. The indicated weight of sulfomethylated agent was then added tosaid Water and was dissolved without the addition of external heat. inpreparing samples A and B the sodium bisulfite and formaldehyde wereadded separately in the amounts indicated. In the remaining samples,stoichiometric amounts of formaldehyde and sodium bisulfite wereprereacted as described elsewhere herein and then added to the water.The indicated volume of sodium hydroxide solution (0.5 gram permilliliter) was then added to the solution with stirring. Heating wasinitiated and the ground quebracho in the amount indicated was addedgradually with stirring, and the addition of heat. The averagetemperature maintained and the reaction time are shown under the headingsulfomethylation reaction. The metal complexing agent(s), if used, wasthen added to the hot solution either dry or in solution as indicated insaid Table V.

Run No.

Base Mud 1 2 3 4 5 6 7 8 Additive:

B,* lbs./bbl. mud 0 3 6 0 0 0 0 0 0 ,*lbs lbbl. mud.-- O 0 0 3 6 0 O 0 0O lbs/Dbl. mud--- 0 0 O 0 0 3 6 0 0 Quebracho 0 0 0 0 0 0 0 3 6 InitialProperties:

Plastic viscosity, cps 18 14 12 17 19 16 14 19 20 Yield point,lbs/10011;. 14 3 5 6 7 8 9 8 7 Initial gel strength, lbs./1001't. 3 2 21 3 4 5 3 3 IO-min. gel strength, lbs/100 ft. 23 3 3 6 7 16 16 12 7 pH9.1 9.1 9.1 7.4 8.4 7.9 8.0 8.9 9.0 Water loss, ml. in min 10. 0 7. 0 5.0 6. 0 4. 4' 9. 2 10. 2 8. 4 7. 6

B*=Iron complex of sulfomethylated quebracho prepared in Example I.

C*=Sulfomethylated quebracho prepared inExaInple I.

Example VI Base mud No. 3 was prepared from base mud N0. 2 of Example Vby adding 5 pounds per barrel of gypsum thereto, as a contaminant.Samples of said base mud No. 3 containing 3 and 6 pounds per barrelrespectively of the sulfomethylated quebracho product of Example I wereprepared for tests. Samples of said base mud containing 3 and 6 poundsper barrel, respectively, of the iron complex of sulfomethylatedquebracho product of Example IV were also prepared for tests. Samples ofsaid base mud No. 3 containing 3 and 6 pounds per barrel respectively ofthe iron complex of sulfornethylated quebracho product of Example I werealso prepared for tests.

Each of said samples was then tested for pH and TABLE IV.ADDTIVES INBASE MUD NO. 3 (20 WT. PERCENT KAOLIN AND 4 WT. PERCENT BENTONI'IEAnother larger scale batch of SMQ-Fe was also prepared. This batch isidentified in Table V below as Sample No. M. In this preparation, 275gallons of Water was added to a 2l0O-gallon reactor tank equipped with adouble-bladed stirring means. A 37 weight percent formaldehyde solutionin the amount of pounds was then added to said water. The resultingsolution was stirred and 1300 pounds of sodium bisulfite was addedthereto over a period of approximately 45 minutes. During this periodthe temperature of the solution increased from about 65 F. to about F.After the reaction between the sodium bisulfite and formaldehyde hadbeen completed, as evidenced by a constant temperature, approximately 35gallons of a 50 weight percent sodium hydroxide solution was added. Thetemperature of the solution increased further to about F. At this time2250 pounds of quebracho were added slowly over 2.

IN WATER PLUS 5 LBS. PER BBL. OF GYPUSM CONTAMINAN'I) Run N0.

Base Mud Additive:

Initial Properties:

B,* lbs/bbl. mud D,* lbs./bbl. mud... CR lbs./bbl. mud Quebracho 10 cocomm ocow emu oooc:

p Water loss, ml. in 30 min H Ii OOCAIO N03 OC7 OO Additives B, D, and 0same in Table II.

13 period of approximately 20 to 25 minutes. During this time thetemperature increased to about 200 F. and the temperature was maintainedwithin the range of 190 to 200 F. for approximately 2 /2 hours. The tankcontents were vigorously agitated during the addition of the quebracho.At this time 1600 pounds of Ferrifloc (a com mercial ferric sulfate)were added slowly over a period of approximately 2 hours with thetemperature remaining within the range of about 190 to about 200 F.After addition of the Ferrifloc was complete the tank contents werecirculated for approximately one hour and then passed to a drum drierfor recovery of the reaction product, i.e., an iron complex ofsulfomethylated quebracho (SMQ-Fe).

The above-described samples of metal complexes of sulfomethylatedquebracho were then used in preparing samples of drilling mud by addingvarious quantities of said additives to one or more of base mud Nos. 4to 7. These drilling mud samples containing the additives of theinvention were all prepared in conventional manner. API Code 29properties were then determined on said drilling mud samples in the samemanner as described in Example III above. Shear strength tests were alsorun employing a Baroid high temperature aging cell or bomb. Briefly,this test comprises placing a sample of the mud to be evaluated in thetest cell or bomb, closing the bomb, and placing same in a hot oil bathor hot air oven maintained at a uniform temperature. After the desiredperiod of aging at the desired temperature, the bomb is cooled to atemperature below 150 F. and opened. A shear tube, made from stainlesssteel, is placed on the surface of the sample and sufiicient gramweights, if necessary, are placed on the tube to start its downwardmotion. Unless too much weight has been placed on the tube, it will stopits downward motion at the point Where the shear strength of the gelledsample against the surface of the tube is sufficient to support theapplied weight. The length of the tube exposed above the sample is thenmeasured. The shear strength in pounds per 100 square feet is obtainedfrom a nomograph by utilizing the force, in grams, applied to the sheartube and the length of exposed tube after the tube reaches equilibrium.Further details of said test can be obtained from Apparatus andProcedure for the Field Testing of Drilling Muds, pp. 90025 and 900-26,Baroid Division, National Lead Co., PO. Box 1675, Houston, Tex. See alsoMeasuring and Interpreting High Temperature Shear Strength of DrillingFluids, Watkins and Nelson, vol. 198, pp. 213- 218, PetroleumTransactions, AIME (1953).

The composition of said base muds, said drilling mud samples, and theresults of tests thereon are set forth in Tables VI to XI below. InTables VII to XI, tests on comparative drilling mud samples containingcommercially available additives of the prior art are also set forth forcomparative purposes.

TABLE V.-PREPARATION SUMMARY: SULFOMETHYLATED QUEBRACHO AND METALCOMPLEXES THEREOF Sulitgnetlgylation Metal Salt v 1 f M 1 eac 1011 o o 0es Sample Vol. Weight Weight "V01. V01. Weight Metal Metal per N0. Egg),NaSOsCHzOH NaHSOa, fliggfo NaiglH, Quebracho, T A W ht 882111:Molnaoiiner ams ams ams ime, vg. erg ou- 0 gr gr ml. gr HL: Temp.,Species Grams tion, Quebracho Min. F. ml.

2a a est 120 0 err 00 40 200 3: 18 187 Alz(SO4) a -18H2O 40 200 3:55 189V205 40 200 2:05 185 MJ1SO4-H O 39 it? 9 5825 8 0 0 1 4- 2 40 200 2:54185 Cl2(SO4)3-5H3O 40 200 2:54 192 CuSO4-5H2O 40 200 2:54 185 ZnSO4-7HzO40 200 4:02 185 T1014 2 600 4:10 189 CuSOl-5HzO 120 600 $10 )198 4 140200 4:08 205 e a z- 2 4 140 200 2:42 200 Or(NOa)a-9HO lFe(N0a)a-9HzO IMilliliters. I 60 grams of solid NaOH added. 5 See paragraph 2 ofExample V1 for d etails. 4 Added in two portions, 40 m1. alter theNaSOzOBhOH was added and 100 ml. after the metal salt solutions.

TAB LE VI.-ADDITIVES IN BASE MUD NO. 4 (20 WT. PERCENT KAOLIN AND 4 WT.PERCENT BENTONITE IN WATER PLUS SUFFICIENT BARITES* TO GIVE MUD WEIGHTOF 12.2 LBSJGAL.

Run Number 1 2 3 4 5 6 7 8 9 10 Base Mud SMQ-Cu SMQ-Zn SMQ-Mn SMQ-CoSMQ,-N1

Additive:

Sample No. (Table V) H H I r I D D E E F F Lbs./bbl. mud O 2. 5 5. 0 2.5 5. 0 2. 5 5. 0 2. 5 5. 0 2. 5 5. 0 Initial Properties: 7

Plastic viscosity, eps 25 24 27 22 25 25 27 25 25 24 25 Yield point,lbs/100 17. 33 4 4 2 1 3 6 4 4 V 4 5 Initial gel, lbs./100 it. 29 2 3 11 2 3 1 2 3 3 IO-min. gel, lbs./100 it)- 3 4 2 2 2 4 7 8 13 11 pH 8. 49.1 9. 0 9. 3 9. 3 9. 1 9. 0 9. 5 9. 2 9. 1 9. 1 After Aging 3 days at,350 F.

Plastic viscosity, cps 28 34 25 26 25 23 24 29 29 25 24 Yield point,lbs/ it]- 35 4 6 9 6 6 5 13 8 24 4 Initial gel, lbs.ll00 ft. 16 2 2 3 33 2 3 3 3 2 10-min. gel, lbs/100 it. I 63 3 7 27 12 13 13 32 19 14 4Water loss, ml./30 min" 10. 2 10.0 10.0 9.8 10.2 11. 6 11. 0 9.8 9. 810.6 10.2

Shear Strength, lbs/100 ftfl. 800 170 160 165 145 340 280 SMQ- Fe-CrQuebracho Q-Broxin SMQ-Al Run Number SMQ-Fe SMQ-Al Run Number SMQ-CuTABLE VI.C0ntinued SMQ-V SMQ Base Mud Additive:

*Commercial product,

a For Runs 19 and 20.

Initial water loss was 0 Initial water loss was Initial Water loss was 9Initial water loss was i Aged at 405 F.

TABLE VII.ADDITIVES IN BASE MUD N0. 5 (6 WT. PERCENT BENTONITE IN WATER)Additive:

Sample No. (Table V)... Lbs./bbl. mud. Initial Properties:

Plastic viscosity, eps Yield point, lbs/100 it?" Initial gel, lbs/100it)" 10-min. gel, lbs/1001M. pH After Aging 3 days at 350 F..

Plastic viscosity, cps.

pH Shear Strength,

Q-Broxiu SMQ-Al Run Number SMQ-Zn SMQ-Fe Base Mud BEN TON IIE IN WATER,PLUS SUFFIGIEN T BARITE* TO GIVE MUD WEIGHT OF 12.2 LBS/GAL.)

Sam le No. (Table V). Lbsfbbl. mud Initial Properties:

Plastic viscosity, cps Yield point, 1bs./ Initial gel, lbs/ it. 10-min.gel, lbs/100 ft).

Plastic viscosity, cps.-. Yield point, lbs/100 ft. Initial gel, lbs/100ft 10-min. gel, lbs/100 13. Wgter loss, ml./30 min p Shear Strength,1bs./1001t. 1, 400 1,

Commercial product. n T=Too thick to measure.

TABLE VIII.-ADDITIVES IN BASE MUD NO. 6 (20 WT. PERCENT P95 ROTARY CLAY(AN ILLITIC CLAY) AND 4W'I. PERCENT Additive:

Quebracho PORTLAND CEMENT) Q-Broxin Run Number CONTAMINATED WITH 2 LBS.[BBL SMQ-Fe Base Mud TABLE IX.ADDITIVES IN BASE MUD NO. 7 (20 WT.PERCENT P95 ROTARY CLAY (AN ILLITIO CLAY) AND 4 WT. PERCENT BENTONITE INWATER,

Sample No. (Table V) LbsJbbl. mud After Agipgi Days at 350 F.:

Additive:

Run Number 1 2 3 4 5 Base 1 Mud SMQ-Fe Carbonox Additive:

Sample No. (Table V) B B B s. mud O 2. 5 5 5 10 Initial Properties:

Plastic viscosit cps 28 21 28 46 12 12 Yield point, lbs/100 ft 33 23 3270 91 76 Initial gel, 1bs./100 it). 28 4 5 34 70 81 10-min. gel, lbs/100(ti. 98 94 104 141 76 84 pH 8.4 8. 3 8. 5 8. 2 8. 3 8. 2 After Aging 3days at 176 F.:

Plastic viscosit cps 33 16 30 13 14 Yield point, lbs/10011; I 54 11 5 1266 69 Initial gel, lbs/100 it]. 46 5 2 5 52 49 10-min gel, lbs/100 it.122 17 18 60 50 Water loss, nil/ min. 9. 8 14.8 4. 8 2.8 36.0 32. 0

Shear Strength, lbs/100 it Not determined on mud samples aged atmoderate temperatures 1 N o contaminant in this mud. Contaminant in mudsamples in Runs 1-5 inclusive.

TABLE XIIL-SMQ-FE IN BASE MUD NO. 8 (60 LB. PER BBL P95 ROTARY CLAY AND12 LB. PER BBL. BENTONITE IN WATER, PLUS 4 VOLUME PERCENT NATURAL BRINE)Drilling mud fluid contained 700 p.p.m. calcium ion and 8,800 p.p.m. ofchloride ion.

Referring to Table VI, the results of tests on ten SMQ- metal complexadditives of the invention are set forth. These results indicate one ofthe outstanding properties of the additives of the invention. The datashow that all of said additives are highly effective dispersing orthinning agents for drilling muds. The results obtained when saiddrilling mud samples were aged for three days at 350 F. are particularlyoutstanding since this represents a very severe test of the gelationcharacteristics of the drilling fluid. The remarkably lower yield point,10-minute gel, and shear strength values obtained on the samplescontaining the additives of the invention, as compared to the values onthe aged base mud, show that the additives of the invention areremarkably eifective in protecting the drilling mud from hightemperature gelation as encountered in high temperature deep wells.

Referring to Table VH, the results there set forth show that theSMQ-metal complex additives of the invention are superior to either SMQalone, the commercially available thinning agent Q-Broxin, or quebracho.

Referring to Table VIII, the results of tests on base mud N0. 6containing SMQ-metal complex additives of the invention are set forth.Due to the type of clay used in preparing base mud No. 6, itsrheological properties are very difficult to control. The test was madeeven more severe by aging the drilling mud samples at the highertemperature of 405 F. The results of the tests show that in allinstances the additives of the invention were efiective in inhibiting orreducing the amount of high temperature gelation. The results of Runs 13and 14 show that the commercial thinning agent Q-Broxin is not aneifective thinner for this mud system.

The results of Run No. 2 in Table VIII are interesting. For some reasonnot presently understood, 10 pounds of the additive SMQ-Fe caused thedrilling mud sample to thicken to the point that the rheologicalproperties could not be measured. However, after said sample was agedthe SMQ-Fe additive was very eifective in thinning the drilling mud.This shows very strikingly the effectiveness of the additives of theinvention as high temperature dispersing or thinning agents. The datashow that, if desired, the concentration of the additive could beincreased as the well becomes deeper. Said data also show that, ifdesired, the drilling mud could be aged before using in the well.

Referring now to Table IX, the results there set forth illustrate theeifectiveness of the additives of the invention in the presence ofcement contamination. The data show that the additive SMQ-Fe, one of thepreferred additives of the invention, is very effective, even in thepresence of cement contamination. Similar results have been observedwith other additives prepared in accordance with the invention. The datain said Table D( also show that the commercial additives Q-Broxin andquebracho are much less effective than the additives of the invention.

Table X sets forth the results of comparative tests between theinvention additive SMQ-Fe and the commercial additive Q-Broxin at threelevels of concentration and for different aging temperatures. Said datashow that the SMQ-Fe additive of the invention is more eifective at alllevels of concentration and at all aging temperatures than was thecommercial additive Q-Broxin.

Tables XI and XII set forth the results of comparative tests betweendrilling mud samples containing a SMQ-Fe additive of the invention andCarbonox, another commercially available thinning agent, at three levelsof concentration. Again, the SMQ-Fe additive of the invention was moreefliective at all levels.

The data set forth in Table XIII show that the additives of theinvention are eifective in the presence of salt contamination.

Example VIII This example illustrates the clay swelling inhibitor actionof the additives of the invention. Compressed pills of bentonite claywere prepared by compressing bentonite in the mold of a pilling machineat a pressure of 24,000 p.s.i. These pills were cylindrical in shape,having a diameter and a length of about /2 inch. Next, a series of glasstubes, closed at one end and having an inside diameter slightly largerthan the diameter of said pills, were fabricated. One pill was insertedinto the bottom of each tube and the height or length of the pill in thetube accurately measured. A series of aqueous test solutions containingvarious amounts of an SMQ-Fe additive of the invention (prepared insubstantially the same manner as Sample B in Table V above) were thenprepared. The pill in each tube was then covered with an excess of oneof said test solutions. Each tube was then placed vertically, open endup, in a bomb containing distilled water in the bottom thereof, tomaintain a water vapor phase during the test. The bombs were sealed, andthen placed in an oven maintained at the temperature indicated in TableXIV below for a period of 18 hours. The bombs were then cooled to roomtemperature, opened, and the length or height of the swelled pillmeasured. A control sample was run at each temperature using distilledWater as the swelling medium.

The swelling index (8.1.) is calculated as follows:

swelling of pill in solution tested sWelling of pill in distilled waterTABLE XVL-SMQ-FE ADDITIVES IN BASE MUD NO. 4 (20 WT. PERCENT KAOLIN ANDWT. PERCENT BENTONITE IN WATER, PLUS SUFFICIENT BARIIES TO GIVE MUWEIGHT OF 12.2 LBSJGAL.)

the method of preparation for these samples was the same as set forth inparagraph one of Example VII above. The amounts of reagents are setforth in Table XV below. The SMQ-Fe products were recovered by drumdrying as in Example VII.

Added in two portions, 40 ml. after the NaSOQCH OH and 300 ml after theFQCL'i-GH O.

Z Added in 700 ml. of water.

Samples of the SMQ-Fe additives were then blended into a base mud toprepare drilling mud samples which were tested as set forth in ExampleVII above. Results of these tests are set forth in Table XVI below.

Run Number 1 2 3 Base Base Mud Mud a SMQ-Fe SMQ-Fe SMQ-Fe Additive:

Sample No. P Q, R Lbs./bbl. mud 10 10 0 Initial Properties:

Plastic viscosity, cps 39 37 65 38 30 Yield point, lbsJlOO ftfi. 62 2385 34 Initial gel, lbs/190 it. 38 12 18 12 36 10-min. gel, lbs/100 n1-75 21 73 Water loss, m1./30 min 8. 5 5. 4 3. 0 8.7 10. 2 pH 8. 2 9. 2 9.l 9.0 8. 4 After Aging 3 days at 350 F.

Plastic viscosity, cps. 34 74 39 41 41 Yield point, lbs/100 it 33 22 918 79 Initial gel, lbs/100 ftfi- 115 4 3 11 63 IO-min. gel, lbs/100 it?166 11 38 122 Water loss, ml./ min 10.2 7.0 8. 8 9. 6 l2. 5 nFI 8.0 8.58.0 8.3 8.1 Shear Strength, lbs/100 it. 500 320 140 475 600 1 Commercialproduct from Baroid Division, National Lead 00.

2 For Runs 1 and 2. 8 For Run 3.

TABLE XIV Run Number SMQ-Fe additive, lbs./bbl. H 0"... 0 1 2 4 6 8 12Swelling Index:

Example IX Three additional samples of SMQ-Fe additive in accordancewith the invention were prepared. In general,

The metal complexes of sulfoalkylated tannin of the invention can beused in a wide variety of aqueous drilling fluids, -e.g., water basedrilling fluids and oil-in-water emulsion drilling fluids. In somewells, particularly where hard limestone formations containing no shaleor clay are being drilled, the drilling fluid can be water containingonly a very small amount of finely divided inorganic solids such as claysolids. Many times the drilling of a well is started with water as thedrilling fluid. As the drilling progresses and shales or clay formationsare penetrated, the circulating water will pick up natural clays andbecome what is commonly referred to as a drilling mud or drilling fluid.In such instances the natural clays can constitute as much as 40 percentby weight of the drilling fluid. More frequently, however, it isdesirable to prepare a drilling fluid which is to be used in thedrilling by mixing a clayey material such as a natural clay or bentonitewith water. If a drilling fluid is thus prepared, the concentration ofthe clayey material is usually lower, generally constituting from about1 to about 25 weight percent of the entire composition. Thus, thedrilling fluids of the invention in which the metal complexes of theinvention are utilized can contain only relatively small amounts of saidclayey materials or can contain said clayey materials in amounts up toabout 40 weight percent of the entire composition.

The finely divided inorganic solids used in the drilling fluids increasethe viscosity and afiord plastering properties to said fluids by aidingthe formation of a filter cake on the wall of the bore hole and thus aidin reducing fluid loss to the formations penetrated by said bore hole.While the presence of said solids is desirable initially, it should bepointed out that the drilling fluids of the invention are operablewithout the initial addition of said solids because a certain solidscontent will develop during the drilling. The finely divided inorganicsolids used in the practice of the invention should be insoluble in theoil phase as well as insoluble in the water phase so that they willremain undissolved over long periods of time. Examples of finely dividedsolids suitable for use in the practice of the invention include, amongothers, the following: bentonite, ground limestone, barites, groundoyster shells, diatomaceous earth, Fullers earth, kaolin, attapulgite,McCracken clay, and other native and/or treated clays. Mixtures of twoor more of said finely divided solids can also be used. Some of saidmaterials such as barites and limestone are used primarily as weightingagents. All of said materials are preferably ground until at least about90 percent with pass through a 325-mesh screen.

A preferred drilling fluid for some drilling operations is anoil-in-water emulsion drilling fluid. These drilling fluids can alsocontain clay or clayey materials in concentrations ranging from smallamounts up to about 40 weight percent. Said oil-in-water emulsiondrilling fluids are usually distinguished from water base drilling bytheir content of from 5 to 40, preferably 5 to 25, weight percent ofoil. However, there is really no sharp dividing line between Water basedrilling fluids and oil-in-water emulsion drillng fluids because waterforms the continuous phase in both. Both are frequently referred to asaqueous drilling fluids. Thus, herein, and in the claims, unlessotherwise specified, the term aqueous drilling fluid is used genericallyand refers to both water base drilling fluids and oil-in-water emulsiondrilling fluids.

In an oil-in-water emulsion drilling fluid, the principal value of theoil is as an aid in controlling the density of the drilling fluid andits fluid loss properties. Oils which can be used in the practice of theinvention are usually petroleum oils, although other oleaginousmaterials such as vegetable and animal oils can be used, though seldomwith economic advantage. The oils in any event should contain at leastsome material boiling above the gasoline boiling range, i.e., aboveabout 400 F. at atmospheric pressure. Oils with too high a content ofhighly volatile hydrocarbons in the gasoline boiling range areundesirable because of the danger of fire, and because of the lowviscosity. It is preferred that the oil have a flash point above about140 F. Examples of suitable oils which can be employed in the practiceof the invention include, among others, the following: topped crude oil,gas oils, kerosene, diesel fuels, heavy alkylates, fraction of heavyalkylates, and the like. The more preferred oils are predominentlyparafiinic in character since these are less detrimental to rubbercomponents in pumps, lines, etc. It is preferred that the oil have agravity within the range of 1540 API.

The aqueous drilling fluids of the invention, both the water basedrilling fluids and the oil-in-water emulsion drilling fluids, cancontain other additives when required to adjust the properties of thedrilling fluids in accordance with conventional practice. Thus, it willbe understood that other additives can be added to the drilling fluidsof this invention without departing from the scope of the invention.Special materials are oftentimes added to drilling fluids for particularpurposes, and such additional materials can be employed in the drillingfluids of this invention, providing a usual and conventional testindicates a lack of obvious adverse reactions, and such additionaladditives are applicable in the drilling fluids of this invention withfew, if any, exceptions.

An important advantage of the metal complex additives of the inventionis the ease with which they can be dispersed in water or in the waterphase of the drilling fluid. Said metal complexes can be incorporated inthe drilling fluids by merely adding same to a stream of the circulatingdrilling fluid. Said metal complexes are easily pulverized solids whichcan be added directly as such to the jet hopper commonly employed informulating drilling fluids. The incorporation of said metal complexesinto the drilling fluid can be either before or during the drilling ofthe well. Thus, said metal complexes of the invention can beincorporated in the drilling fluid in any suitable manner.

While certain embodiments of the invention have been described forillustrative purposes, the invention obviously is not limited thereto.Various other modifications will be apparent to those skilled in the artin view of this disclosure. Such modifications are within the spirit andscope of the invention.

I claim:

1. An aqueous well drilling fluid comprising a mixture containing water,suflicient suspended finely divided solids to form a filter cake on thewall of the well, and an amount of a metal complex of a sulfoalkylatedtannin sufficient to reduce at least one of (a) the water loss due tofiltration through said filter cake, ('b) the yield point, and (c) the10-minute gel of said drilling fluid, but insufficient to increase theviscosity of said drilling fluid to such an extent that it cannot becirculated, said metal complex having been prepared by theinter-reaction between a tannin compound selected from the groupconsisting of the gallotannins and the flavotannins, in an alkalineaqueous reaction medium at a temperature within the range of from 70 to300 F. and in amounts based on parts by weight of said tannin compound,from 1 to 60 parts by weight of a carbonyl compound selected from thegroup consisting of the lower molecular weight aldehydes and ketones,from 4 to parts by weight of a sulfur compound selected from the groupconsisting of sulfurous acid and water-soluble salts thereof, and from0.3 to 64 parts by weight of a metal selected from the group consistingof iron, copper, chromium, nickel, cobalt, manganese, zinc, aluminum,titanium, vanadium, and mixtures thereof, said metal being present in acompound selected from the group consisting of the hydroxides and thewater-soluble salts of said metals.

2. An aqueous drilling fluid according to claim 1 wherein the amount ofsaid metal complex in said drilling fluid is within the range of from0.1 to 30 pounds per barrel of said drilling fluid.

3. An aqueous drilling fluid according to claim 1 wherein the amount ofsaid metal complex in said drilling fluid is within the range of from 1to 15 pounds per barrel of said drilling fluid.

4. An aqueous drilling fiuid according to claim 2 wherein said metal isiron and the parts by weight thereof is within the range of from 6 to20, said tannin compound is quebracho extract, said carbonyl compound isformaldehyde and the parts by weight thereof is Within the range of from15 to 36, said sulfur compound is sodium 'bisulfite and the parts byweight thereof is within the range of from 35 to 65, and said metalcomplex is prepared by reacting said quebracho extract with saidformaldehyde and said sodium bisulfite to form sulfomethylatedquebracho, and said iron compound is reacted with said sulfomethylatedquebracho toform an iron complex of sulfomethylated quebracho.

5. An aqueous drilling fluid according to claim 1 wherein said metal iscopper and the parts by weight thereof is within the range of from 6.5to 21, said tannin compound is quebracho extract, said carbonyl compoundis formaldehyde and the parts by weight thereof is within the range offrom 15 to 36, said sulfur compound is sodium bisulfite and the parts byweight thereof is within the range of from 35 to 65, and said metalcomplex is prepared by reacting said quebracho extract with saidformaldehyde and said sodium bisulfite to form sulfomethylatedquebracho, and said copper compound is reacted with said sulfomethylatedquebracho to form a copper complex of sulfomethylated quebracho.

6. An aqueous drilling fluid according to claim 1 wherein said metal ischromium and the parts by weight thereof is within the range of from 5.8to 17, said tannin compound is quebracho extract, said carbonyl compoundis formaldehyde and the parts by weight thereof is within the range offrom 15 to 36, said sulfur compound is sodium bisulfite and the parts byweight thereof is within the range of from 35 to 65, and said metalcomplex is prepared by reacting said quebracho extract with saidformaldehyde and said sodium bisulfite to form sulfomethylatedquebracho, and said chromium compound is reacted with saidsulfomethylated quebracho to form a chromium complex of sulfomethylatedquebracho.

7. An aqueous drilling fluid according to claim 2 wherein said metal isaluminum and the parts by Weight thereof is within the range of from 3to 9, said tannin compound is quebracho extract, said carbonyl compoundis formaldehyde and the parts by weight thereof is within the range offrom 15 to 36, said sulfur compound is sodium bisulfite and the parts byweight thereof is within the range of from 35 to 65, and said metalcomplex is prepared by reacting said quebracho extract with saidformaldehyde and said sodium bisulfite to form sulfomethylatedquebracho, and said aluminum compound is reacted with saidsulfomethylated quebracho to form an aluminum complex of sulfomethylatedquebracho.

8. An aqueous drilling fluid according to claim 2 wherein said metal iszinc and the parts by weight thereof is within the range of from 6.7 to22, said tannin compound is quebracho extract, said carbonyl compound isformaldehyde and the parts by weight thereof is within the range of from15 to 36, said sulfur compound is sodium bisulfite and the parts byweight thereof is within the range of from 35 to 65, and said metalcomplex is prepared by reacting said quebracho extract with saidformaldehyde and said sodium bisulfite to form sulfomethylatedque'bracho, and said Zinc compound is reacted with said sulfomethylatedquebracho to form a zinc complex of sulfomethylated quebracho.

9. In a process for the drilling of a well with well drilling toolswherein there is circulated in said well a drilling fluid, theimprovement comprising circulating in said well in contact with the wallthereof an aqueous well drilling fluid comprising a mixture containingwater, sufficient suspended finely divided solids to form a filter cakeon the wall of the well, and to which drilling fluid there has beenadded an amount of a metal complex of a sulfoalkylated tannin sufficientto reduce at least one of (a) the water loss due to filtration throughsaid filter cake, (b) the yield point, and (c) the 10-minute gel of saiddrilling fluid, but insufficient to increase the viscosity of saiddrilling fluid to such an extent that it cannot be circulated, saidmetal complex having been prepared by the inter-reaction between atannin compound selected from the group consisting of the gallotanninsand the flavotannins, in an alkaline aqueous reaction medium at atemperature within the range of from 70 to 300 F. and in amounts basedon 100 parts by weight of said tannin compound, from 1 to 60 parts byweight of a carbonyl compound selected from the group consisting of thelower molecular weight aldehydes and ketones, from 4 to 115 parts byWeight of a sulfur compound selected from the group consisting ofsulfurous acid and water-soluble salts thereof, and from 0.3 to 64 partsby weight of a metal selected from the group consisting of iron, copper,chromium, nickel, cobalt, manganese, zinc, aluminum, titanium, vanadium,and mixtures thereof, said metal being present in a compound selectedfrom the group consisting of the hydroxides and the water-soluble saltsof said metals.

10. A process according to claim 9 wherein the amount of said metalcomplex in said drilling fluid is within the range of from 0.1 to 30pounds per barrel of said drilling fluid.

11. A process according to claim 9 wherein said metal is iron and theparts by weight thereof is within the range of from 6 to 20, said tannincompound is quebracho extract, said carbonyl compound is formaldehydeand the parts by weight thereof is within the range of from 15 to 36,said sulfur compound is sodium bisulfite and the parts by weight thereofis within the range of from 35 to 65, and said metal complex is preparedby reacting said quebracho extract with said formaldehyde and saidsodium bisulfite to form sulfomethylated quebracho, and said ironcompound is reacted with said sulfomethylated quebracho to form an ironcomplex of sulfomethylated quebracho.

12. A process according to claim 9 wherein said metal is copper and theparts by weight thereof is within the range of from 6.5 to 21, saidtannin compound is quebracho extract, said carbonyl compound isformaldehyde and the parts by weight thereof is within the range of from15 to 36, said sulfur compound is sodium bisulfite and the parts byweight thereof is within the range of from 35 to 65, and said metalcomplex is prepared by reacting said quebracho extract with saidformaldehyde and said sodium bisulfite to form sulfomethylatedquebracho, and said copper compound is reacted with said sulfomethylatedquebracho to form a copper complex of sulfomethylated quebracho.

13; A process according to claim 9 wherein said metal is chromium andthe parts by weight thereof is within the range of from 5.8 to 17, saidtannin compound is quebracho extract, said carbonyl compound isformaldehyde and the parts by weight thereof is within the range of from15 to 36, said sulfur compound is sodium bisulfite and the parts byweight thereof is within the range of from 35 to 65, and said metalcomplex is prepared by reacting said quebracho extract with saidformaldehyde and said sodium bisulfite to form sulfomethylatedquebracho, and said chromium compound is reacted with saidsulfomethylated quebracho to form a chromium complex of sulfomethylatedquebracho.

14. A process according to claim 9 wherein said metal is aluminum andthe parts by weight thereof is within the range of from 3 to 9, saidtannin compound is quebracho extract, said carbonyl compound isformaldehyde and the parts by weight thereof is within the range of from15 to 36, said sulfur compound is sodium bisulfite and the parts byweight thereof is within the range of from 35 to 65, and said metalcomplex is prepared by reacting said que bracho extract with saidformaldehyde and said sodium bisulfite to form sulfomethylatedquebracho, and said aluminum compound is reacted with saidsulfomethylated quebracho to form an aluminum complex of sulfomethylatedquebracho.

15. A process according to claim 9 wherein said metal is zinc and theparts by weight thereof is within the range of from 6.7 to 22, saidtannin compound is quebracho extract, said carbonyl compound isformaldehyde and the parts by weight thereof is within the range of from15 to 36, said sulfur compound is sodium bisulfite and the parts byWeight thereof is within the range of from 35 to 65, and said metalcomplex is prepared by reacting said quebracho extract with saidformaldehyde and said sodium bisulfite to form sulfomethylatedquebracho, and said zinc compound is reacted with said sulfo- 27 28methylated quebracho to form a zinc complex of sulfo- 2,653,967 9/1953Monroe 260-473.5 methylated quebracho. 3,034,982 5/1962 Monroe 2528.53,065,039 11/1962 Komarek et a1. 894.24 References Cited FOREIGN PATENTSUNITED STATES PATENTS 5 2,603 1/1899 Great Britain. 2,092,622 9/1937Koch et a1. s 94.24 2,331 2 1 10 1943 Wayne 25 3 5 LEON ROSDOL, PrimaryExaminer- 2,605,221 7/1952 Hoeppel 252-8.5 H. B. GUYNN, AssistantExaminer.

1. AN AQUEOUS WELL DRILLING FLUID COMPRISING A MIXTURE CONTAINING WATER,SUFFICIENT SUSPENDED FINELY DIVIDED SOLIDS TO FORM A FILTER CAKE ON THEWALL OF THE WELL, AND AN AMOUNT OF A METAL COMPLEX OF A SULFOALKYLATEDTANNIN SUFICIENT TO REDUCE AT LEAST ONE OF (A) THE WATER LOSS DUE TOFILTRATION THROUGH SAID FILTER CAKE, (B) THE YIELD POINT, AND (C) THE10-MINUTE GEL OF SAID DRILLING FLUID, BUT INSUFFICIENT TO INCREASE THEVISCOSITY OF SAID DRILLING FLUID TO SUCH AN EXTENT THAT IT CANNOT BECIRCULATED, SAID METAL COMPLEX HAVING BEEN PREPARED BY THE INNER-REACTONBETWEEN A TANNIN COMPOUND SELECTED FROM THE GROUP CONSISTING OF THEGALLOTANNINS AND THE FLAVOTANNINS, IN AN ALKALINE AQUEOUS REACTIONMEDIUM AT A TEMPERATURE WITHIN THE RANGE OF FROM 70 TO 300*F. AND INAMOUNTS BASED ON 100 PARTS BY WEIGHT OF SAID TANNIN COMPOUND, FROM 1 TO60 PARTS BY WEIGHT OF A CARBONYL COMPOUND SELECTED FROM THE GROUPCONSISTING OF THE LOWER MOLECULAR WEIGHT ALDEHYDES AND KETONES, FROM 4TO 115 PARTS BY WEIGHT OF A SULFUR COMPOUND SELECTED FROM THE GROUPCONSISTING OF SULFUROUS ACID AND WATER-LOLUBLE SALTS THEREOF, AND FROM0.3 TO 64 PARTS BY WEIGHT OF A METAL SELECTED FROM THE GROUP CONSISTINGOF IRON, COPPER, CHROMIUM, NICKEL, COBALT, MANGANESE, ZINC, ALUMINUM,TITANIUM, VANADIUM, AND MIXTURES THEREOF, SAID METAL BEING PRESENT IN ACOMPOUND SELECTED FROM THE GROUP CONSISTING OF THE HYDROXIDES AND THEWATER-SOLUBLE SALTS OF SAID METALS.